Process for the oxidation of ticl4



United States Patent 3,340,008 PROCESS FOR THE OXIDATION OF TiCl Earl William Nelson, Lynchburg, and John Peter Wikswo,

Amherst, Va., assignors to American Cyanamid Company, Stamford, Conn., a corporation of Maine N0 Drawing. Filed Feb. 17, 1965, Ser. No. 433,507 6 Claims. (Cl. 23-202) ABSTRACT OF THE DISCLOSURE This invention relates to a process of reacting titanium tetrachloride with an oxygen-containing gas by means of diametrically opposed reactant streams to form two opposed parallel laminar flames, said reactant streams containing carbon monoxide and water in an amount equal to 0.005 to 0.05% by volume of the total gas feed.

This invention relates to an improved method of burning TiCl to produce T iO pigment.

In the manufacture of TiO pigment by the combus tion of TiCl it has been proposed that a small amount of water should be present during the combustion reaction for the purpose of nucleating the formation of TiO pigment particles. The systems in which water is employed as a nucleating agent have required a minimum of .05% by volume of water, based on the total combustion mixture, becausewithout the minimum amount of water, the nucleating effect is not obtained. Contrary to the finding that at least .05% by volume of water must be used in order to obtain a nucleating effect, we have discovered unexpectedly that in a system utilizing carbon monoxide, the nucleating eflect of water is not detectable and the quantity of water to be used for the purpose of obtaining a beneficial effect is substantially less. It was surprising that the use of water in amounts less than .05% by volume produces a beneficial effect, because according to prior workers no benefit with water is possible below that critical amount.

It is apparent from the work done with carbon monoxide that the benefit of using water arises from a catalytic eflect rather than a nucleating effect. The relatively smaller amounts of water used for the purpose of the present invention serve to catalyze the combustion of CO to CO with a consequent control over the rate of heat release that is beneficial to produce quality. The benefit of water in the present invention is essentially non-existent if the water is generated in situ during the combustion of TiCl, to pigmentary material. We believe that water generated in situ is not formed in time to catalyze the combustion of CO to CO so that the desired heat release occurs at an optimum time with respect to the combustion reaction of TiCl to TiO The lack ofbenefit from water generated in situ for the combustion reaction is another indication of how the present invention differs from those systems in which the combustion of TiCl is accomplished without CO being present. The nature of the present invention willbe described in greater detail hereinbelow in order to provide a better understanding of it. I

Accordingly, an object of this invention is to provide an improved method of producing T iO pigment.

Another object of this invention is to provide an improved method of reacting TiCl with oxygen in the presence of CO.

Other objects and advantages of this invention will become apparent from the following description and explanation thereof.

By means of the present invention, TiCl and C0 are reacted with oxygen in the presence of a very small ice amount of water. The combustion of TiCl is conducted at a temperature of about 1400 to 1850 C., more usually about 1450 to 1600 C. The volumetric ratio of CO to TIC14 is about 0.1 to 3.021, and more usually about 0.3 to 10:1. The water content of the total feed mixture being charged to the combustion zone is about .005 to .06% by volume, more usualy about .02 to 04% by volume. The volumetric space velocity of the total feed mixture at the inlet to the combustion Zone, determined as the cubic feet per minute of feed mixture being fed to the combustion zone per square foot of flow area of the burner inlet (measured at the inlet of the combustion zone), is about 15 to 45 and more usually about 20 to 35. The volume of total feed material is measured at 25 C. and one atmosphere of pressure. While the combustion reaction occurs satisfactorily under essentially atmospheric pressure, a higher or lower pressure may be employed. The oxygen-containing gas, measured as the excess over the stoichiometric amount needed to react with all the TiCl, and also assuming that a stoichiometric amount of oxygen is present to react with all the CO, is about 5 to 120% excess on a volumetric basis, and more usually about 40 to 80% on the same basis. Aluminum chloride is also fed to the combustion reaction in an amount of about 1 to 5% by weight, more usually about 2 to 3 by weight, measured as A1 0 in the TiO product.

The advantages of the present invention are readily realized when the combustion reaction is conducted in a laminar flow burner of the type described in Patent No. 3,121,641. The apparatus and method of operation described in the aforesaid patent are hereby incorporated by reference and made a part of the present specification. In a laminar burner, the feed material is divided into two main streams which are introduced into the burning zone from diametrically opposed directions. The flames issuing from each feed point oppose each other and form two adjacent parallel continuous flame fronts which contact each other without significant intermixing of materials between the flames. The introduction of the total feed mixture may be accomplished in a variety of ways, however, it is preferred that each feed stream pass through a series of dampening screens which serve to reduce any tendency toward flow turbulence. The feed material may also be preheated to a temperature of about 180 to 300 C., and more usually about 200 to 250 C.

The oxygen present in the combustion reaction may be supplied as a pure oxygen material or as air or enriched air. For reasons of efliciency of operation, it is preferred that pure oxygen be used as the source of supply for the combustion reaction. We have also discovered that relatively large excesses of oxygen in the combustion reaction have a beneficial effect on the formation of pigmentary material. For reasons not clearly understood it appears that large excesses of oxygen serve to promote the forma-' tion of pigment product. Consequently, to obtain such added advantage, it is contemplated practicing the present invention with an excess amount of oxygen ranging from about to 12%. When excess oxygen is used as a promoter, it may be possible to reduce the amount of aluminum chloride and/or water to be employed in the reaction. The mass action effect created by the use of large excesses of oxygen diminishes the need for the apparent catalytic effect exerted by the small amount of Water being used in the reaction, however, the catalytic effect of water is still present even when using large excesses of oxygen.

Water is added to the reaction by any suitable means or method. If desired, water may be injected directly into the total feed mixture or any one or more of the feed components may be partly or wholly saturated with water to provide the required amount for the reaction. In practice, it is preferred to pass the CO stream through a humidifier in order that an intimate association of the two materials can be accomplished. Since the water serves as a catalyst for the combustion of the CO, admixing the CO 4 carbon monoxide to titanium tetrachloride being about 0.1 to 3.0: 1, the amount of oxygen being a stoichiometric excess of about 5 to 120% by volume and the volumetric space velocity of the total gas at the inlet to the combusand water reduces the possibility that water might not be 5 b 15 t 45 f available to serve as a catalyst during the combustion re- Zone emg 0 cub1c eat per mmutes Per square action. The CO stream may be passed through a humidifier foot of flow area of the bufner mletwherein its water content may be adjusted to about 200 to 2. The Process of etalm 1 whel'elll the oxygen 4000 p.p.m., and more usually about 1200 to 1800 p.p.m. taining gas is oxygen. y e the amount Of Water added the 0 tr 1O 3. The process of claim 1 being further characterized w ll provide a fina concenthration based on the totalbfeed by the additional presence of about 1 to 5% aluminum mixturecorrespon ing to t e amount given herema ove. chloride measured as A1203 in the final pigment.

Aluminum chloride may be added to the T1Cl feed. 4 I f 1 The mixture of the two chlorides is then vaporized at a n a proces? reactmg tltamum tetrach f Wlt temperature of about 140 C. to 250 C., and more usuan oxygen comalnmg gas by means of dlamemcany ally about 175 C. to 200 C., and at a pressure of about Posed reactant streams to form two pp Parallel 1 to 120 p.s.i.g., more usually about to 45 p.s.i.g. The laminar flames, the improvement which comprises reactvaporous admixture of aluminum chloride and TiCl m y ing said materials in the presence of carbon monoxide and be teadlly combtfled t the other teed componentsend a small amount of water in an amount of about 0.02 to fi P g gli f i a g i 20 0.04% by volume of the total gas, at a temperature of ereula W 1e a ummum c on 6 may a e 0 about 1450 to 1600 C., the volumetric ratio of carbon the T1Cl in an amount of about 1 to 5 by weight, more usually about 2 to 3% by Weight measured as A1203 in monoxide to titanium tetrachloride being about 0.3 to the T10 product, it should be understood that a larger Loil, the amount of Oxygen bemg a Stowhlomemc f or smaller amount of aluminum chloride may be used cess of about 40 to by Volume, and the Volumetric in the combustion reaction with a consequent advantage. space velocity of the total gas being about 20 to cubic To provide a better understanding of the present invenfeet per minute per square foot of flow area of the burner tion, experiments were made in a burner of the type deinlet. g? In t f 93 3 35 the reaction 30 5. The process of claim 4 being further characterized con Hons S Own a e e mc u mg a reaction by the additional presence of about 1 to 5% aluminum pressure of essentially one atmosphere. The burner tubes hl d Al O h fi h d t employed in the experiments reported below were 15 inch c on 6 measure as 3 m t 6 6 plgmen tubes and the feed gases were introduced into the burner The PfeeeSS 0f elalm 4 Wherelh the Oxygen-Contamtubes without the tangential swirl. The hood of the burner taining gas is oxygen. was aluminum lined with insulating brick, which replaced 35 the cooling jacket shown in the patent.

TABLE I RunNo 12|3'4l5 TiCh, 1b mol/hr 3.2 3.2 3.2 3.2 3.0 3-0 Oxygen, molar excess, percent 80 80 80 80 100 100 CO/TiCh, molar ratio 55 55 55 70 70 Vol. space velocity 31 31 31 31 31 31 H20, vol. percent (total feed .0002 0063 .0124 0307 .0002 .0071 Combustion temp, 1,505 1,505 1,505 1, 505 1, 545 1, 545 Pigment quality (as burned):

Tint tone V Br r Brs Bri V B! V Tinting strength 1,420 1,580 1, 590 720 1,230 Pigment Quality (ground) Tint tone B17 Br, Br; V Br V Br Tinting strength 1,510 1, 640 1, 650 820 1, s20

l The TiCl; contains 3 mol percent A101 2 Milled for eight minutes in a 2-wheel chaser mill with 100 pounds of force on each wheel.

We claim:

1. In a process for reacting titanium tetrachloride with posed reactant streams to form two opposed parallel laminar flames, the improvement which comprises reacting said materials in the presence of carbon monoxide and a small amount of water in an amount of about .005 to .05 percent by volume of the total gas feed, at a tempera- References Cited UNITED STATES PATENTS 2,635,946 4/1953 Weber et al 23202 X 2,915,367 12/1959 Olson et al 23202 2,957,753 10/ 1960 Nelson et a1. 23-202 2,980,509 4/ 1961 Frey 23-202 3,069,282 12/1962 Allen 23202 X 3,121,641 2/1964 Wiksmo et a1 23202 X OSCAR R. VERTIZ, Primary Examiner.

ture of about 1400 to 1850 C., the volumetric ratio of EDWARD STERN: Examiner" UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,340 ,008 September 5 1967 Earl William Nelson et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 7, for "usualy" read usually line 58, for "12%" read 120% Signed and sealed this 18th day of February 1969.

(SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents Edward M. Fletcher, Jr.

Attesting Officer 

1. IN A PROCESS FOR REACTING TITANIUM TETRACHLORIDE WITH AN OXYGEN CONTAINING GAS BY MEANS OF DIAMETRICALLY OPPOSED REACTANT STREAMS TO FORM TWO OPPOSED PARALLEL LAMINAR FLAMES, THE IMPROVEMENT WHICH COMPRISES REACTING SAID MATERIALS IN THE PRESENCE OF CARBON MONOXIDE AND A SMALL AMOUNT OF WATER IN AN AMOUNT OF ABOUT .005 TO .05 PERCENT BY VOLUME OF THE TOTAL GAS FEED, AT A TEMPERATURE OF ABOUT 1400* TO 1850*C. THE VOLUMETRIC RATIO OF CARBON MONOXIDE TO TITANIUM TETRACHLORIDE BEING ABOUT 0.1 TO 3.0:1 THE AMOUNT OF OXYGEN BEING A STOICHIOMETRIC EXCESS OF ABOUT 5 TO 120% BY VOLUME AND THE VOLUMETRIC SPACE VELOCITY OF THE TOTAL GAS AT THE INLET TO THE COMBUSTION ZONE BEING 15 TO 45 CUBIC FEET PER MINUTES PER SQUARE FOOT OF FLOW AREA OF THE BURNER INLET. 